1. Field of the Invention
The present invention relates to animal feed additives comprising disalts of formic acid. The invention further comprises animal feedstuff containing said additives.
A general problem with feed additives comprising monocarboxylic acids, and especially formic acid, are loss of acid due to evaporation. This causes an off-spec product and corrosion problems in the equipment for making the feed and is also hazardous to those handling the additive and the feedstuff. Another problem is making additives that are free-flowing and which easily can be mixed with the other ingredients of the feedstuff. The additives must also be stable during storage and able to endure the temperatures they are exposed to during production of the feed, without decomposing.
2. Description of the Related Art
Application and effects thereof of monocarboxylic acids like formic acid and formates like calcium formate in animal feedstuff are generally known in the art. The effects of these additives have been found to give increased growth rate, improvements of feed conversion and reduced diarrhoea frequency. Thus it is known from EP 0317668 A1 that promoted growth of piglets can be achieved by applying a conventional fodder containing 5-25% of a dry mixture containing 3-5 parts of calcium formate. Said dry mixture further contains 1-25 parts fat, 18-28 parts protein, 13-20 parts minerals, 3-5 parts citrate and 30-50 parts lactose. However, this additive does have some disadvantages and limitations of use. Calcium formate has a low water solubility and can only be used in limited amounts to avoid too high total content of calcium in the feed. The concentration of formate in the additive is rather low and the effect is only of the same order of magnitude or lower as when formic acid is added to the feed. This is further shown in an article by M. Kirchgessner and F. X. Roth, "Use of formates in the feeding of piglets", Landwirtsch. Forschung 40, 2-3, 1987. On page 149 it is stated that "Cafo (calcium formate) influenced the feed consumption of the piglets only slightly; the animals improved feed conversion at about 5% at the highest dose levels (2.7/2.6% Cafo)".
From EP 219997 is further known a preservative composition for adding to animal feedstuff comprising a binary blend of formic acid and propionic acid with synergistic activity. The aqueous blend of acids is impregnated in a solid carrier such as silica. 0.1-10% of the blend is used in feed for pigs, cattle or poultry. One disadvantage of the additive is that the percentage of active agent on the carrier is rather low. Further, due to the poor thermal stability of the product the risk for losing some of the acid during production and storage is rather high and thereby the effective cost of the active substance is increased. The impregnated carrier might also cause damage to the equipment and those being exposed to the product due to leakage/evaporation of acid from the carrier.
The nutritive effect of fumaric acid by varying the protein quality and protein content of the feed on fattening performance of broilers is described in an article in Archiv fur Geflugelkunde 1991, 55 (5) pages 224-232, Eugen Ulmer & Co, Stuttgart, Germany. On the average fumaric acid seemed to improve final live weight by 3.9% and feed conversion by 2.6%, whereas the feed intake was not affected. The nutritive effect on weight gains decreased from 4.2-2% during the several growth periods. Feed utilisation changed from 3 over 2 to 2.5%. The increase in efficiency of the organic acid related to the lower nutrient supply was more pronounced only in period 0-14 days.
In the product data sheet for PRESCO International there is described application of the additive "Formic Spray" (formic acid on a carrier) in amounts of 0.5-1.5% in feedstuff for piglets, pigs, cows, broilers and layers. Said additive is stated to improve in general the efficiency of feedstuff for these animals. This additive has, however, experienced a considerable loss of formic acid during storage.
In GB Patent No. 1.505.388 there is described formation of aqueous solutions of complex salts from ammonium ions and/or of a metal selected from Group I and II of the Periodic Table and at least one carboxylic acid. The ratio of acid to ammonium and/or metal ions being in the range of 2:1 and 4:1 on a chemical equivalent basis. The concentration of water in the aqueous solution being between 15-75% by weight of the total composition. Said solution of complex salts or disalts of carboxylic acids is stated to be a preservative composition to prevent growth of mould, bacteria and fungi and therefor useful in animal feed which in the patent is also named "substrate". When applied as a preservative to a substrate the liquid composition suitably contains between 0.1-5% of the inorganic complex acid salt based on the weight of the substrate treated. The only example relating to use of formates is ammonium diformate in silage which is not the same type of animal feedstuff which the present application relates to. Ammonium diformate is the most unstable of all the diformates and the teachings of this patent does not give any teaching for application of diformates except for silage and similar types of feedstuff and then in connection with prevention/reduction of growth of mould, fungi and bacteria.